I recently compared the 1920s Klan to the religious right (Alec Ryrie’s Misinformation about the KKK). Slate (here) just compared the 1920s Klan to Breitbart and the alt-right. These are two sides of the same coin. Again, the Klan of the 1920s was a large, mainstream group. We can learn a lot from it, though it is often misrepresented. Again, I recommend Wyn Wade’s, The Fiery Cross.